1. Field of Invention
The present invention relates to ultrathin ferromagnetic/antiferromagnetic coupling film structures and fabrication methods thereof, and more particularly, to a ferromagnetic/antiferromagnetic coupling film structure used in a multilayer film of a spin valve and a fabrication method thereof.
2. Description of Related Art
Recording media can be divided in terms of recording means into 4 groups: magnetic recording, optical recording, magneto-optical recording and semiconducting recording media. Among them, magnetic recording and optical recording media are the two mainly used. Giant magnetoresistance (GMR), which is shown in a magnetical multilayer film formed by alternate growth of ferromagnetic layers and non-ferromagnetic layers, has been used in read head and attracted extensive researches, and a spin valve multilayer film having the exchange coupling effect is considered to be the most potential system.
The spin valve multilayer film structure includes antiferromagnetic layer/ferromagnetic layer I/spacer layer/ferromagnetic layer II, wherein the exchange coupling effect between the antiferromagnetic layer and the ferromagnetic layer is a key property in a spin valve system. Generally, in a research of the exchange magnetic anisotropy between the ferromagnetic layer and the antiferromagnetic layer, the ferromagnetic layer is generally made of a ferromagnetic 3d transition metal such as Fe, Co or NiFe. There are four groups of antiferromagnetic layers, i.e. (1) ferromagnetic metal oxides, such as CoO film and NiO film; (2) alloys made of Mn and ferromagnetic metals such FeMn film, NiMn film and CoMn film; (3) alloys made of Mn and other transition metals such as PtMn film, PdMn film and IrMn film; and (4) other metal films such as FeF2.
Exchange bias coupling was found from Co and tiny particles on the oxide layer. Furthermore, antiferromagnetic films formed by insulating transition metal oxides such as CoO film and NiO film have simple and stable chemical and magnetic structures, and also have excellent anticorrosive and anti-oxidative properties. Accordingly, the antiferromagnetic film can be used in a spin valve system for preventing the current shunting effect.
However, it is still desired to have an ultrathin ferromagnetic/antiferromagnetic film structure used in a spin valve multilayer film structure and a fabrication method thereof.